scholarly journals Numerical Simulation of Overland Flows Using Godunov Scheme Based on Finite Volume Method

10.29007/nbs4 ◽  
2018 ◽  
Author(s):  
Dawei Zhang ◽  
Jin Quan ◽  
Zhili Wang ◽  
Hongbin Zhang ◽  
Jianming Ma
Keyword(s):  
Numerical Models ◽  
Flow Sheet ◽  
Godunov Scheme ◽  
Overland Flows ◽  
Small Depth ◽  
Highly Nonlinear ◽  
Coarse Meshes ◽  
Volume Method ◽  
Steep Slopes ◽  
Accurate Numerical Solution

A new numerical model for simulating overland flows has been developed using Godunov scheme based on the two-dimensional fully dynamic shallow water equations (SWEs). There are a number of frequently and partially submerged cells due to steep slopes, coarse meshes and small depth when simulating the surface runoff propagation, which are different from the original hydraulic applications such as flooding. In order to provide an accurate numerical solution for overland flows, the model in this work uses the Roe’s approximate Riemann solver for the calculation of fluxes on the triangulated unstructured grid based on the flow sheet regime, and the bottom slope terms are calculated directly by applying the Green’s theorem. To control the global stability of the model, the semi-implicit discretization method is adopted to deal with the highly nonlinear friction terms. The new model provides more comprehensive calculation capabilities, which are proved by several case studies, and the numerical results match well with analytical solutions, experimental data or results computed by other numerical models.

scholarly journals Research on Hydroelastic Response of an FMRC Hexagon Enclosed Platform

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1110
Author(s):  
Wei-Qin Liu ◽  
Luo-Nan Xiong ◽  
Guo-Wei Zhang ◽  
Meng Yang ◽  
Wei-Guo Wu ◽  
...  
Keyword(s):  
Time Domain ◽  
Numerical Models ◽  
Structural Response ◽  
Deep Ocean ◽  
Surface Model ◽  
Large Area ◽  
Floating Structure ◽  
Small Depth ◽  
Response Amplitude Operators ◽  
Hydroelastic Response

The numerical hydroelastic method is used to study the structural response of a hexagon enclosed platform (HEP) of flexible module rigid connector (FMRC) structure that can provide life accommodation, ship berthing and marine supply for ships sailing in the deep ocean. Six trapezoidal floating structures constitute the HEP structure so that it is a symmetrical very large floating structure (VLFS). The HEP has the characteristics of large area and small depth, so its hydroelastic response is significant. Therefore, this paper studies the structural responses of a hexagon enclosed platform of FMRC structure in waves by means of a 3D potential-flow hydroelastic method based on modal superposition. Numerical models, including the hydrodynamic model, wet surface model and finite element method (FEM) model, are established, a rigid connection is simulated by many-point-contraction (MPC) and the number of wave cases is determined. The load and structural response of HEP are obtained and analyzed in all wave cases, and frequency-domain hydroelastic calculation and time-domain hydroelastic calculation are carried out. After obtaining a number of response amplitude operators (RAOs) for stress and time-domain stress histories, the mechanism of the HEP structure is compared and analyzed. This study is used to guide engineering design for enclosed-type ocean platforms.

scholarly journals An Analytical and Numerical Study of Magnetic Spring Suspension with Energy Recovery Capabilities

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3126 ◽  
Author(s):  
Yu Jia ◽  
Shasha Li ◽  
Yu Shi
Keyword(s):  
Energy Recovery ◽  
Numerical Study ◽  
Numerical Models ◽  
Limited Range ◽  
Paradigm Shifts ◽  
Restoring Force ◽  
Highly Nonlinear ◽  
Spring Mechanism ◽  
Paved Road ◽  
Rider Comfort

As the automotive paradigm shifts towards electric, limited range remains a key challenge. Increasing the battery size adds weight, which yields diminishing returns in range per kilowatt-hour. Therefore, energy recovery systems, such as regenerative braking and photovoltaic cells, are desirable to recharge the onboard batteries in between hub charge cycles. While some reports of regenerative suspension do exist, they all harvest energy in a parasitic manner, and the predicted power output is extremely low, since the majority of the energy is still dissipated to the environment by the suspension. This paper proposes a fundamental suspension redesign using a magnetically-levitated spring mechanism and aims to increase the recoverable energy significantly by directly coupling an electromagnetic transducer as the main damper. Furthermore, the highly nonlinear magnetic restoring force can also potentially enhance rider comfort. Analytical and numerical models have been constructed. Road roughness data from an Australian road were used to numerically simulate a representative environment response. Simulation suggests that 10’s of kW to >100 kW can theoretically be generated by a medium-sized car travelling on a typical paved road (about 2–3 orders of magnitude higher than literature reports on parasitic regenerative suspension schemes), while still maintaining well below the discomfort threshold for passengers (<0.315 m/s 2 on average).

Non-Newtonian Fluid Flow Analysis with Finite Difference and Finite Volume Numerical Models

2001 ◽  
Vol 11 (6) ◽  
pp. 325-335
Author(s):  
Jure Marn ◽  
Marjan Delic ◽  
Zoran Zunic
Keyword(s):  
Finite Difference ◽  
Finite Volume ◽  
Numerical Models ◽  
Flow Analysis ◽  
Mesh Size ◽  
Newtonian Flow ◽  
Driven Cavity ◽  
Commercial Code ◽  
Fluid Flow Analysis ◽  
Volume Method

Abstract Suitability of finite difference method and finite volume method for computation of incompressible non newtonian flow is analyzed. In addition, accuracy of numerical results depending of mesh size is assessed. Both methods are tested for driven cavity and compared to each other, to results from available literature and to results obtained using commercial code CFX 4.3.

scholarly journals Dealing with deep uncertainties in landslide modelling for disaster risk reduction under climate change

2017 ◽  
Vol 17 (2) ◽  
pp. 225-241 ◽  
Author(s):  
Susana Almeida ◽  
Elizabeth Ann Holcombe ◽  
Francesca Pianosi ◽  
Thorsten Wagener
Keyword(s):  
Slope Stability ◽  
Slope Failure ◽  
Numerical Models ◽  
Landslide Risk ◽  
Residual Soils ◽  
Loss Of Life ◽  
Economic Changes ◽  
Critical Thresholds ◽  
Stability Model ◽  
Steep Slopes

Abstract. Landslides have large negative economic and societal impacts, including loss of life and damage to infrastructure. Slope stability assessment is a vital tool for landslide risk management, but high levels of uncertainty often challenge its usefulness. Uncertainties are associated with the numerical model used to assess slope stability and its parameters, with the data characterizing the geometric, geotechnic and hydrologic properties of the slope, and with hazard triggers (e.g. rainfall). Uncertainties associated with many of these factors are also likely to be exacerbated further by future climatic and socio-economic changes, such as increased urbanization and resultant land use change. In this study, we illustrate how numerical models can be used to explore the uncertain factors that influence potential future landslide hazard using a bottom-up strategy. Specifically, we link the Combined Hydrology And Stability Model (CHASM) with sensitivity analysis and Classification And Regression Trees (CART) to identify critical thresholds in slope properties and climatic (rainfall) drivers that lead to slope failure. We apply our approach to a slope in the Caribbean, an area that is naturally susceptible to landslides due to a combination of high rainfall rates, steep slopes, and highly weathered residual soils. For this particular slope, we find that uncertainties regarding some slope properties (namely thickness and effective cohesion of topsoil) are as important as the uncertainties related to future rainfall conditions. Furthermore, we show that 89 % of the expected behaviour of the studied slope can be characterized based on only two variables – the ratio of topsoil thickness to cohesion and the ratio of rainfall intensity to duration.

scholarly journals Fire Resistance of Axially Loaded Slender Concrete Filled Steel Tubular Columns – Development of a Three-Dimensional Numerical Model and Comparison with Eurocode 4

10.14311/1089 ◽  
2009 ◽  
Vol 49 (1) ◽  
Author(s):  
A. Espinós ◽  
A. Hospitaler ◽  
M. L. Romero
Keyword(s):  
Numerical Model ◽  
Fire Resistance ◽  
Numerical Models ◽  
Three Dimensional ◽  
Calculation Model ◽  
Construction Technology ◽  
Tubular Columns ◽  
Highly Nonlinear ◽  
Structural Engineers ◽  
Simplified Calculation

In recent years, concrete filled tubular (CFT) columns have become popular among designers and structural engineers, due to a series of highly appreciated advantages: high load-bearing capacity, high seismic resistance, attractive appearance, reduced column footing, fast construction technology and high fire resistance without external protection. In a fire, the degradation of the material properties will cause CFT columns to become highly nonlinear and inelastic, which makes it quite difficult to predict their failure. In fact, it is still not possible for analytical methods to predict with enough accuracy the behaviour of columns of this kind when exposed to fire. Numerical models are therefore widely sought. Many numerical simulations have been carried out worldwide, without obtaining satisfactory results. This work proposes a three-dimensional numerical model for studying the actual fire behaviour of columns of this kind. This model was validated by comparing the simulation results with fire resistance tests carried out by other researchers, as well as with the predictions of the Eurocode 4 simplified calculation model. 

scholarly journals Finite Element and Finite Volume Modelling of Friction Drilling HSLA Steel under Experimental Comparison

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 5997
Author(s):  
Bernd-Arno Behrens ◽  
Klaus Dröder ◽  
André Hürkamp ◽  
Marcel Droß ◽  
Hendrik Wester ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Material Flow ◽  
Numerical Models ◽  
Rolling Direction ◽  
Experimental Comparison ◽  
Drilling Process ◽  
Friction Drilling ◽  
Volume Method

Friction drilling is a widely used process to produce bushings in sheet materials, which are processed further by thread forming to create a connection port. Previous studies focused on the process parameters and did not pay detailed attention to the material flow of the bushing. In order to describe the material behaviour during a friction drilling process realistically, a detailed material characterisation was carried out. Temperature, strain rate, and rolling direction dependent tensile tests were performed. The results were used to parametrise the Johnson–Cook hardening and failure model. With the material data, numerical models of the friction drilling were created using the finite element method in 3D as well as 2D, and the finite volume method in 3D. Furthermore, friction drilling tests were carried out and analysed. The experimental results were compared with the numerical findings to evaluate which modelling method could describe the friction drilling process best. Highest imaging quality to reality was shown by the finite volume method in comparison to the experiments regarding the material flow and the geometry of the bushing.

Highly Nonlinear Solitary Waves to Estimate Orientation and Degree of Anisotropy in Rocks

2021 ◽  
Vol 79 (10) ◽  
pp. 991-1004
Author(s):  
Hoda Jalali ◽  
Yuhui Zeng ◽  
Piervincenzo Rizzo ◽  
Andrew Bunger
Keyword(s):  
Solitary Waves ◽  
Numerical Models ◽  
Spherical Particles ◽  
Highly Nonlinear ◽  
Degree Of Anisotropy ◽  
Highly Nonlinear Solitary Waves ◽  
Rock Interface ◽  
Nondestructive Identification ◽  
Nonlinear Solitary Waves

This paper delves into the use of highly nonlinear solitary waves for the nondestructive identification and characterization of anisotropy in rocks. The nondestructive testing approach proposed expands upon a technique developed recently by some of the authors for the nondestructive characterization of engineering materials and structures. The technique uses the characteristics of solitary waves propagating in a periodic array of spherical particles in contact with the rock to be characterized. The features of the waves that bounce off the chain rock interface are used to infer some properties of the geomaterial under consideration. Numerical models and experimental validation were conducted to explore the feasibility of the method and to standardize the methodology for future widespread applications.

Predictive Capability of a 2D FNPF Fluid-Structure Interaction Model

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Solomon C. Yim ◽  
Huan Lin ◽  
David C. Robinson ◽  
Katsuji Tanizawa
Keyword(s):  
Free Surface ◽  
Numerical Models ◽  
Fluid Structure Interaction ◽  
Nonlinear Behavior ◽  
Degree Of Freedom ◽  
Surface Boundary ◽  
Predictive Capability ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Highly Nonlinear

The predictive capability of two-dimensional (2D) fully-nonlinear-potential-flow (FNPF) models of an experimental submerged moored sphere system subjected to waves is examined in this study. The experimental system considered includes both single-degree-of-freedom (SDOF) surge-only and two-degree-of-freedom (2DOF) surge-heave coupled motions, with main sources of nonlinearity from free surface boundary, large geometry, and coupled fluid-structure interaction. The FNPF models that track the nonlinear free-surface boundary exactly hence can accurately model highly nonlinear (nonbreaking) waves. To examine the predictive capability of the approximate 2D models and keep the computational effort manageable, the structural sphere is converted to an equivalent 2D cylinder. Fluid-structure interaction is coupled through an implicit boundary condition enforcing the instantaneous dynamic equilibrium between the fluid and the structure. The numerical models are first calibrated using free-vibration test results and then employed to investigate the wave-excited experimental responses via comparisons of time history and frequency response diagrams. Under monochromatic wave excitations, both SDOF and 2DOF models exhibit complex nonlinear experimental responses including coexistence, harmonics, subharmonics, and superharmonics. It is found that the numerical models can predict the general qualitative nonlinear behavior, harmonic and subharmonic responses as well as bifurcation structure. However, the predictive capability of the models deteriorates for superharmonic resonance possibly due to three-dimensional (3D) effects including diffraction and reflection. To accurately predict the nonlinear behavior of moored sphere motions in the highly sensitive response region, it is recommended that the more computationally intensive 3D numerical models be employed.

Nonlinear Dynamic Behaviour of the Intervertebral Disc

2013 ◽  
Author(s):  
Giacomo Marini ◽  
Gerd Huber ◽  
Stephen J. Ferguson
Keyword(s):  
Dynamic Response ◽  
Intervertebral Disc ◽  
High Frequency ◽  
Nonlinear Dynamic ◽  
Mechanical Response ◽  
Numerical Models ◽  
Low Frequency ◽  
Upper Body ◽  
Highly Nonlinear ◽  
Flexion Extension

The intervertebral disc, like many collagen-based tissues, has a mechanical response which is highly nonlinear (1). This characteristic is due to both the arrangement and composition of the tissue constituents of the disc (2). Over the past decades several studies have reported the nonlinear response of the disc for different loading scenarios. In particular, past studies were focused on the quasi-static and low frequency (< 10Hz) response to pure and combined cyclic loading, such as axial compression, shear, flexion/extension moment (3–6). The information provided by these studies has been applied in several fields, from the validation of numerical models to the development of disc prostheses. However, such loading conditions are only partially representative of the in-situ load that the intervertebral disc normally experiences. High frequency dynamics stimuli, such as that experienced while driving a car on a rough surface or driving heavy industrial machinery, are also important. It is well known that long-term exposure to vibrational loading is detrimental to normal disc metabolism (7,8). Despite its relevance only a few studies have investigated the dynamic response of the disc to high frequency vibration (9,10) with sometimes different outcomes. In particular, no study has shown an asymmetric, nonlinear dynamic behavior of the system, even though it is evident in quasi-static testing — the well-known tension / compression asymmetry. This aspect is somehow neglected when building rigid body models of the upper body for impact simulation where a Kelvin-Voigt model with linear stiffness is normally used. The aim of this experimental study was therefore to investigate the nonlinear dynamic response of the intervertebral disc to high frequency loadings, taking different pre-loads and displacement amplitude into account.

scholarly journals Heat Transfer Potentiality and Flow Behavior in a Square Duct Fitted with Double-Inclined Baffles: A Numerical Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Amnart Boonloi ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Numerical Models ◽  
Flow Behavior ◽  
Square Duct ◽  
Square Channel ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Commercial Code ◽  
Volume Method

Numerical analysis of heat transfer mechanisms and flow topologies for the heat exchanger square channel (HESC) installed with the double-inclined baffles (DIB) is reported. The main objective of the present research is to study the influences of DIB height to duct height ( b / H = 0.05 – 0.30 ), DIB distance to duct height ( P / H = 1 – 1.5 ), and flow attack angle ( α = 30 °   and   45 ° ) on the flow topologies, heat transfer features, and thermal performances. The Reynolds numbers (based on the entry HESC around 100–2000) are analyzed for the present problem. The numerical models of the HESC installed with the DIB are solved with finite volume method (commercial code). The simulated results of the HESC installed with the DIB are reported in forms of flow topologies and heat transfer characteristics. The Nusselt numbers (Nu), friction factors ( f ), and thermal enhancement factors (TEF) of the HESC placed with the DIB are offered. As the numerical results, it is seen that the DIB produces the vortex streams and impinging streams in all cases. The vortex streams and impinging streams disturb the thermal boundary layer on the HESC walls that is a key motive for the growth of heat transfer rate. The best TEF of the HESC installed with the DIB is about 3.87 at P / H = 1 , α = 30 ° , Re = 2000 , and b / H = 0.15 . Additionally, the TEF contours, which help to design the HESC inserted with the DIB, are performed.

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